...it was denied that the [CT 66] number was picked as a reminder of a former television program entitled Highway[sic] 66.
There have been several US 6A's in the state, all gone now:
Newtown - Southbury (1955 - 1966)
Church Hill and Glen Roads in Newtown, crossing the Housatonic River into Southbury, were originally part of US 6; US 6A was created in 1955 when a new US 6/US 202 highway opened to the south (which is now part of I-84). This US 6A is now unposted SR 816.
Plymouth - Hartford (1932 - 1942)
At first, this US 6A followed present-day US 6 from the Route 72 junction through Bristol to Route 10 in Farmington. In 1934, it was extended eastward along the Colt Highway, South Street, and Brown Street to the old US 5 (Maple Avenue) in Hartford, taking over part of Route 71. US 6 at the time used Farmington Avenue. In 1943 or 1944, this US 6A became part of the relocated US 6, which now crossed the Connecticut River using the new Charter Oak Bridge.
Woodbury - Willimantic (Jan. 1, 1941 - 1967)
The longest US 6A, this was created from the westernmost 59 miles of Route 14, which served Waterbury, Meriden, and Middletown. It was a much better route cross-state than US 6 at the time. In the 1950s, the state started planning an expressway for US 6A, which eventually became Interstate 691. As I-84 opened, the western portion of US 6A became less important, and in 1967 all of US 6A was broken into Routes 64, Route 322, and Route 66, as well as local streets in Meriden and Waterbury. Signs were changed in East Hampton on Jan. 10, 1968.
Coventry-Windham (1940 - 1942)
Until 1940, US 6 went through Coventry instead of Andover, along part of today's Route 31. In 1940, US 6 was moved to its current "Suicide 6" path from Bolton to Columbia; the Coventry route became a short-lived US 6A. In 1942, this US 6A became Route 31.
Killingly (1959 - 1968)
Now the Danielson Pike (SR 607/SR 618), this northern loop out of Danielson was part of US 6 until the divided highway section opened. US 6A was turned over to "secret" SR 607 in 1968.
Plymouth - Manchester (proposed, but never signed)
A 1968 plan to reroute US 6 through New Britain, Rocky Hill and possibly Glastonbury would leave behind several miles of existing US 6. A proposed designation for that portion was US 6A.
In the early 1940s, there was a bit of '6A overload': the Woodbury - Willimantic US 6A was paralleled by the Plymouth and Coventry US 6A's.
Now only one US alternate route exists in the state: US 1A in Stonington.